Hydraulic control

ABSTRACT

A hydraulic control which incorporates an elongate fluid containing tube having diaphragms mounted at each end thereof for actuation due to movement of the fluid in the tube. One or both of the diaphragms are used to mechanically actuate hydraulic valves for controlling a mechanism. Movement of the tube about a central transverse pivot will cause gravity flow of the fluid toward the lower diaphragm moving it outwardly while simultaneously moving the upper diaphragm an equal amount inwardly. The tube is mounted on the device to be controlled and the hydraulic mechanism is used to return the device to a position in which the two diaphragms are equi-spaced outwardly from the tube. The tube is such that when used with high speed devices centrifugal force will cause the outer diaphragm to be raised and the inner diaphragm lowered with respect to the curve that the device is moving through. In this instance the hydraulic mechanism may be used to bank the device as long as the centrifugal force is operating on the tube. In one modified form of the invention a thermal expansion &amp; diaphragm action displacement resilient bag replaces the diaphragm not used for valve control.

United States Patent [191 McMullen 1 June 26, 1973 1 1 HYDRAULIC CONTROL Wayne W. McMullen, 1055 NW.

93rd Lane. Coon Rapids. Minn. 55433 221 Filed: Nov. 6, 1970 21 Appl. No.: 87,442

[76] Inventor:

[52] US. Cl 200/83 R, 200/83 Y, 251/61,

303/24 R [51] Int. Cl H0111 35/34, F16k 31/165 [58] Field of Search 200/83 R, 83 B, 83 D,

200/83 Y, 81.5, 61.52, 83 F, 83 N, 153 W, 81 R; 303/24 R; 251/61, 309

Primary ExaminerRobert K. Schaefer Assistant ExaminerRobert A. Vanderhye Attorney-John E. McGarry [5 7 ABSTRACT A hydraulic control which incorporates 'an elongate fluid containing tube having diaphragms mounted at each end thereof for actuation due to movement of the fluid in the tube. One or both of the diaphragms are used to mechanically actuate hydraulic valves for controlling a mechanism. Movement of the tube about a central transverse pivot will cause gravity flow of the fluid toward the lower diaphragm moving it outwardly while simultaneously moving the upper diaphragm an equal amount inwardly. The tube is mounted on the device to be controlled and the hydraulic mechanism is used to return the device to a position in which the two diaphragms are equi-spaced outwardly from the tube. The tube is such that when used with high speed devices centrifugal force will cause the outer diaphragm to be raised and the inner diaphragm lowered with respect to the curve that the device is moving through. In this instance the hydraulic mechanism may be used to bank the device as long as the centrifugal force is operating on the tube. In one modified form of the invention a thermal expansion & diaphragm action displacement resilient bag replaces the diaphragm not used for valve control.

HYDRAULIC CONTROL BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to the control of the level of devices such as ground, water, and air vehicles.

SUMMARY OF THE INVENTION The present invention incorporates an elongate hollow fluid tube having diaphragms connected to each end thereof for actuation by movement of the fluid in the tube. One or both of the diaphragms are connected to control valves for hydraulic mechanisms which control the level of the device on which the tube is mounted so as to move the device and the tube to re turn the device to a predetermined level condition. The movement of the fluid in the tube is controlled by gravity as the tube is tilted or by centrifugal force when the tube is mounted on a high speed device rounding a curve. In the case of centrifugal force the control can be used to cause the vehicle to bank into the curve. In the case where only one diaphragm controls the valve, the other may be replaced by a resilient thermal expansion displacement bag.

The primary object of the invention is to provide a hydraulic mechanism control which senses out of level conditions as well as conditions of centrifugal force and causes the device on which it is mounted to assume a desired condition of tilt.

Other objects and advantages will become apparent in the following specification when considered in the light of the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of the invention shown partially broken away for convenience of illustration;

FIG. 2 is a transverse cross-section taken along the line 22 of FIG. 1, looking in the direction of the arrows;

FIG. 3 is an enlarged fragmentary side elevation taken along the line 33 of FIG. 2, looking in the direction of the arrows;

FIG. 4 is a fragmentary front elevation of the structure illustrated in FIG. 3;

FIG. 5 is a fragmentary top plan view of the invention partially broken away for the convenience of illustration;

FIG. 6 is a fragmentary vertical sectional view taken along the line 6-6 of FIG. 5, looking in the direction of the arrows;

FIG. 7 is an enlarged vertical sectional view of the control valve taken along the line 77 of FIG. 5, looking in the direction of the arrows;

FIG. 8 is a view similar to FIG. 7 showing the valve in a different position;

FIG. 9 is a rear elevation partially broken away illustrating the control hydraulic circuits of the invention;

FIG. 10 is a fragmentary side elevation of the invention partially broken away for convenience of illustration;

FIG. 11 is a vertical sectional view of a modified form of the invention with each of the diaphragms connected to control valves;

FIG. 12 is a diagrammatic view of one form that the hydraulic circuits may take in utilizing the modification illustrated in FIG. 11; and I FIG. 13 is a view similar to FIG. 11 of a modified form of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings in detail wherein like reference characters indicate like parts throughout the several figures the reference numeral 20 indicates generally a hydraulic control system constructed in accordance with the invention.

The hydraulic control system 20 is illustrated in FIGS. 1 through 10 as attached to and controlling a conventional road grader 21. The system 20 is however useful with a wide variety of mechanical equipment.

The road grader 21 includes a frame 22 supported on drive wheels 23 and steerable wheels 24. An engine 25 is supported on the road grader for powering the drive wheels 23.

A frame 26 is secured to the frame 22 by a draw bar 27 which is connected to the forward end of the frame 22 adjacent and between the steerable wheels 24. A mouldboard circular frame 28 is mounted beneath the frame 26 for adjustment about a vertical axis. A pair of depending arms 29 are secured at their upper ends to the circular frame 28 and have a transverse mouldboard 30 secured thereto. The road grader 21 as described above is of conventional design and the mouldboard 30 is normally operated with one end, normally called the toe, forward of the other end, normally called the heel.

An elongate hollow tube 31 extends transversely of the road grader 21 and is secured to the frame 26 by a longitudinal pivot pin 32. A elbow 33 is integrally formed with the tube 31 and has a generally cylindrical cup 34 integrally secured to the elbow 33. A 90 elbow 35 is integrally secured to the opposite end of the tube 31 and has a generally cylindrical cup 36 integrally secured thereto. The axes of the cups 34, 36 are arranged in spaced parallel relation.

A flexible diaphragm 37 extends across the top of the cup 34 and is secured thereto by a mounting ring 38. A circular cover 39 is secured to the ring 38 in spaced relation to the diaphragm 37. A plurality of axially extending bores 40 open through the ring 38 to permit a flow of air therethrough and the escape of water. The cover 39 has a central bore 41 through which a shaft 42 extends. The shaft 42 projects through the diaphragm 37 and has a pair of circular metallic plates 43, 44 mounted thereon on opposite sides of the diaphragm 37.

A hydraulic valve 45 is rigidly secured to the cover 39 by a bracket 46. A lever 47 for actuating the valve 45 extends toward the shaft 42 and is connected thereto by a swivel connection 48. Vertical movement of the diaphragm 37 will move the shaft 42 vertically and rotate the lever 47 to thus rotate the plug 49 of the valve 45.

The valve 45 is a fourway rotary spool valve with closed center and with zero lap in the neutral position. This valve is of the type often referred to as a tracer valve.

The valve 45 includes a generally cylindrical body 50 within which the plug 49 rotates. A pressure connection 51 extends through the body 50 and a cylinder connection 52 extends through the body 50 adjacent the pressure connection 51. A cylinder connection 53 extends through the body 50 and a reservoir connection 54 extends through the body 50 between the cylinder connection 52 and the cylinder connection 53. The plug 49 has a flattened portion 55 formed thereon and a adjacent flattened portion 56 also formed thereon. A third flattened portion 57 is formed on the plug 69 substantially oppositely of the flattened portion 55. A bore 54 extends through the plug 49 from the flattened portion 55 to the flattened portion 57 to provide communication therebetween.

As can be seen in FIG. 7 with the plug 49 in one position the pressure connection 51 communicates with the cylinder connection 52 across the flattened portion 55 while the cylinder connection 53 communicates with the reservoir connection 54 across flattened portion 56. With the plug 49 in a second position the pressure connection 51 communicates with the cylinder connection 53 through the bore 58 and the cylinder connection 52 communicates with the reservoir connection 54 across the flattened portion 56. It can be thus seen that the valve 45 provides means for pressuring one side of a hydraulic cylinder while simultaneously bleeding the opposite side thereof to reservoir.

A flexible diaphragm 59 is secured to the cup 36 by means of an annular ring 60 mounted thereon. A circular cover 61 is secured to the annular ring 60 in spaced apart relation to the diaphragm 59 and has a central bore 62 formed therein. A plurality of vent holes 63 extend through the ring 60 to drain off trapped water from the top of the diaphragm 59. The tube 31, cup 34, and cup 36 are completely filled with fluid 64 so that no air is trapped below the diaphragm 37 or the diaphragm 59. From this it can be seen that any movement of the fluid 64 in the tube 31 will cause the diaphragms 37, 59 to move oppositely-Should the tube 31 be tilted out of level so that the diaphragm 37 is lower than the diaphragm 59 the fluid 64 will flow toward the diaphragm 37 moving it upwardly as seen in FIG. 6 while simultaneously the diaphragm 59 will move downwardly.

A bracket 65 is mounted on one end of the mouldboard 30 and has a rotary valve 66 secured thereto. The valve 66 is identical to the valve 415 and has a shaft 67 extending outwardly therefrom connected to a feeler arm 68 which is adapted to ride on a stake mounted wire 69 used to establish the grade elevation, to be cut by the mouldboard 30. A crank arm 70 is pivotally mounted in a bracket 71 carried by the frame 22. A link 72 is pivotally connected to the crank arm 70 and to one side of the frame 26. A second crank arm 73 is pivotally mounted in a bracket 74 carried by the frame 22 and a link 75 is pivotally connected to the crank arm 73 and to one side of the frame 26 oppositely of the link 72.

A hydraulic ram 76 is mounted on the frame 22 and has the piston rod 77 thereof connected to the crank arm 70 to rotate the crank arm 70 upon actuation of the hydraulic ram 76. Rotation of the crank arm 70 will move the link 72 up and down causing the frame 26 to raise and lower on the side connected to the link 72.

A second hydraulic ram 78 is mounted on the frame 22 oppositely of the hydraulic ram 76 and has the piston rod 79 thereof connected to the crank arm 73 to rotate the crank arm 73 upon actuation of the ram 78. The link 75 connecting the crank arm 73 to the frame 26 will cause the frame 26 to raise and lower to follow the movement of the crank arm 73. A pair of conduits 80, 81 extend to opposite ends of the hydraulic ram 76 to carry the operating hydraulic fluid thereto. A pairof conduits 82, 83 extend to the hydraulic rams 78 to carry the hydraulic operating fluid thereto.

A crank arm extension 84 is secured to the crank arm 73 by U bolts 85. The extension 8 1 has an elongate slot 86 formed therein and a bracket 87 is secured to the extension 84 bya bolt 88 which extends through the slot 86 so that the bracket 87 may be adjusted longitudinally of the extension 84. A gear box 89 is mounted on the bracket 87 and has a threaded shaft 90 depending therefrom. A bracket 91 is secured to the tube 31 adjacent the cup 36 and has a hollow member 92 pivotally secured thereto. The hollow member 92 has a nut 93 secured to the upper end thereof throughwhich the threaded shaft 90 extends. A flexible shaft 94 extends from the hand crank 95 to the gear box 89 so that the threaded shaft is driven thereby to increase and decrease the distance between the hollow member 92, the bracket 87 thus adjusting the relative distance between the crank arm 73 and the tube 31. As the operator turns the crank in a direction to lower the hollow member 92, the heel of the mouldboard 30 continues to rise and thus raises the crank arm 73 so that in fact the tube 31 remains level. Thus it can be seen that adjustments with the crank 95 vary the height of the heel of the mouldboard 30 to adjust the slope of the mouldboard.

A hydraulic pump 96 is mounted on the grader 21 and is connected by a conduit 97 to a reservoir 98. A conduit 99 extends from the pump 96 to a hand controlled valve 100. The hand control valve 100 is connected to a T coupling 101 connected to the reservoir return line conduit 102. A conduit 103 extends from the valve 100 to a conventional flow divider 104. The hand control valve 100 is used to provide pressure into the conduit 103 or to block it from flowing therethrough, and divert the flow back to the reservoir 98 through T coupling 101 and return it to reservoir 98 through conduit 102 thus simply circulating the fluid from the pump 96 through conduit 99 and back to the reservoir 98. The flow divider is provided with a conduit 105 which extends to a hand control valve 106. The hand control valve 106 is identical to the valve 100 and these are conventional hydraulic valves. A reservoir conduit 107 extends from the valve 106 to a T coupling 108. A conduit 109 extends from the valve 106 to the valve 66 where it is connected to the pressure connection 51. A conduit 110 extends from the T coupling 108 to the reservoir connection 54. A conduit 1 11 extends from the cylinder connection 52 to a valve 112. A conduit 113 extends from the cylinder connection 53 to the valve 112.

The valve 112 is a double acting cylinder pilot check valve of'the type manufactured by Racine Hydraulic and Machinery Inc., of Sarasota, Florida under the code number 1606-2. A conduit 114 extends from one side of the valve 112 to the upper end of the hydraulic ram 76. A conduit 115 extends from the opposite side of the valve 112 to the lower end of the hydraulic ram 76. The valve 112 is a lock valve which prevents the flow of hydraulic fluid from the ram 76 through either of the conduits 114, 115 except when pressure is applied through either the conduit 111 or the conduit 113. In the event that either the hand valve 100 or the hand valve 106 is closed so that no pressure exist in the conduits 111, 113. The valve 112 remains completely closed so that the hydraulic ram 76 may be operated through the conduits 80, 81, 82 and 83 in the usual manner. a

A conduit 116 extends from the flow divider 104 to the pressure connection 51 of the valve 45. A conduit 117 extends from the reservoir connection 54 to a T coupling 118 connected by a conduit 119 to the T coupling 108 and by a conduit 120 to the T coupling 101. A conduit 121 extends from the cylinder connection 52 to a valve 122. A conduit 123 extends'from the cylinder connection 53 of the valve 45 to the valve 122. The valve 122 is identical in every respect to the valve 112 and a conduit 124 extends from the valve 122 to the upper end of the hydraulic rams 78. A conduit 125 extends from the valve 122 to the lower end of the hydraulic ram 78. The valve 122 closes both the conduits 124 and 125 except when pressure reaches the valve 122 through one of the conduits 121, 123 so that the hydraulic ram 78 may be operated when either of the valves 100, 106 are closed by utilizing the conventional control C of the grader 21. The valves 112, 122 additionally function to permit the conventional controls to be used at any time to override the automatic controls regardless of whether valves 100 and 106 are open or closed. If the pump 96 stopped supplying pressure to the automatic system the valves 112 and 122 prevent any hydraulic fluid from escaping from the cylinders 76, 78 into the conduits 111, 113, 121 or 123. As an example, the operation of valve 112 is such that before hydraulic fluid can escape out of cylinder 76 through conduit 115 into conduit 113, pressure must be first applied to valve 112 through conduit 111.

In the use and operation of the system 20 as illustrated in FIGS. 1 through the grader 20 is positioned along side of a guide wire 69 with the arms 68 in contact with the top of the guide wires 69. The mouldboard 30 is adjusted to have the desired transverse angle by varying the hydraulic rams 76, 78 with the conventional hand controls. The tube 31 is then adjusted with the hand crank 95 so that it is level and the grader 21 then moves along the roadway with the arms 68 riding on the wire 69. If the mouldboard 30 rises with respect to the wire 69 the arm 68 drops down feeding fluid from the conduit 109 through the valves 66 to the conduit 113 and conduit 115 to the lower end of the hydraulic ram 76. This causes the piston rod 77 to move outwardly lowering the links 72 and the toe end of the mouldboard 30. In the event that the mouldboard 30 drops, the arm 68 is raised and the opposite side of the hydraulic ram 76 is pressurized to raise the link 72.

As one side of the frame 26 is raised and lowered by the hydraulic ram 76 the level of the fluid filled tube 31 changes so that the fluid shifts from side to side. The displacement of this fluid moved by gravity or centrifugal force moves the diaphragm 37 upwardly or downwardly in the cup 34 to actuatethe valve 45. The movement of the diaphragm 37 causes the valve 45 to power the hydraulic ram 78 in a direction to move the frame 26 to cause the tube 31 to return to its level position.

The tube 31 always extends transversely of the grader 21 where as the mouldboard 30 extends at an angle to the direction of level. The angle of the mouldboard 30 can be adjusted by rotating the frame 28 from the frame 26 and hence the amount of raising and lowering of the heel end of the mouldboard 30 will vary with respect to the tube 31 substantially depending upon the transverse angle. By adjusting the bracket 87 in the slot 86 of the extension 84 the effect of movement of the crank arm 73 can be varied widely so that the heel of the mouldboard 30 can be raised or lowered the de sired amount in order to maintain the desired angle in the mouldboard 30 as the toe of the mouldboard 30 is moved vertically by the wire 69.

In FIGS. 11 and 12 a modified form of the invention is illustrated wherein a generally horizontal tube 131 is provided with an integral elbow 133 at one end having a generally cylindrical cup 134 integrally formed thereon. A 90 elbow 135 is integrally formed on the opposite end of the tube 131 and has a generally cylindrical cup 136 integrally formed thereon. A diaphragm 137 is secured across the top of the cup 134 by means of a ring 138 mounted thereon. A generally flat circular cover 139 is secured to the ring 138 parallel to the diaphragm 137 and spaced upwardly therefrom. A bore 141 opens centrally of the cover 139 and a shaft .142 extends therethrough. A pair of circular plates 1.43

and 144 are positioned on the lower and upper faces respectively of the diaphragm 137 and are secured thereto on the shaft 142. A rotary valve 145 is mounted on a bracket 146 secured to the cover 139 and has an operating arm 147 extending outwardly therefrom. A swivel connection 148 connects the shaft 142 to the arm 147 so that the rotary valve 145 is rotated upon vertical movement of the diaphragm 137. A filling tube 149 is mounted on the cup 134 and is closed with a screw plug 150.

The cup 136 has an identical diaphragm 137 secure therein by a ring 138. The cup 136 is closed by a cover 139 and a valve 145 is secured to the cover 139 with a bracket 146. The arm 147 of the valve 145 is connected by a swivel coupling 148 to the shaft 142 of the diaphragm 137 so that thevalve 145 at each end of the tube 131 is actuated by movement of the diaphragm 137. The valves 145 are identical to the valve 45 described in the preferred embodiment of the invention. The tube 131 is fluid tilled and gravity or centrifugal forces move the fluid from side to side to raise and lower the diaphragms 137 in the same manner as the diaphragm 37 is moved in the preferred form of the invention.

In FIG. 12 a hydraulic pump 196 is connected by a conduit 197 to a reservoir 198 and on the opposite side to a flow divider 204. The flow divider 204 provides pressure fluid to each of the valves 145 and these are in turn connected to opposite ends of a hydraulic ram R through a double acting cylinder pilot check valve 212 identical to the valve 112 described in the preferred embodiment of the invention.

While the double diaphragm system of FIG. 11 has been illustrated'as connected to a single hydraulic ram it should be understood that the valves 145 at each end thereof, may be connected to separate hydraulic rams to accomplish the same function.

While the invention has been described above with respect to a fluid tube in which the fluid moves due to gravity as the tube is tilted it should be understood that in high speed devices the hydraulic rams may be used to bank the device due to movement of the fluid under centrifugal force in the tube.

The system 20 may be applied to many different mechanisms such as selfpropelled scrapers, blacktop laydown or asphalt finishers, spreader boxes, slip form pavers, curb laying machines, back hoes, shovels, front end loaders, land levelers, side hill combines, highway slope mowing tractors, tractor mounted hay stackers,

farm tractors, semi-trailers, automobiles, submarine stabilizers, army tanks, all terrain vehicles, aircraft ailerons, and various forms of material handling machines such as fork lift trucks.

In FIG. 13 another modified form of the invention is illustrated generally wherein an elongate hollow tube 231 extends transversely of a device to be controlled. A 90 elbow 233 is integrally formed with the tube 231 and has a generally cylindrical cup 234 integrally secured thereto. A 90 elbow 235 is integrally secured to the opposite end of the tube 231 and has a second 90 elbow 236 integrally secured thereto in a generally S form with the elbow 235.

A flexible diaphragm 237 extends across the top of the cup 234 and is secured thereto by a mounting ring 238. A circular cover 239 is secured to the ring 238 in spaced relation to the diaphragm 237. A plurality of axially extending bores 240 open through the ring 238 to permit a flow of air therethrough and the escape of water. The cover 239 has a central bore 241 through which a shaft 242 extends. The shaft 242 projects through the diaphragm 237 and has a pair of circular metallic plates 243, 244 mounted thereon on opposite sides of the diaphragm 237.

A hydraulic valve 245 is rigidly secured to the cover 239 by a bracket 246. A lever 247 for actuating the valve 245 extends toward the shaft 242 and is connected thereto by a swivel connection 2418. Vertical movement of the diaphragm 237 will move the shaft 242 vertically and rotate the lever 247 to thus rotate the plug 249 of the valve 245.

The valve 245 is a fourway rotary spool valve with closed center and with zero lap in the neutral position. This valve is of the type often referred to as a tracer valve.

A box 259 is secured to the elbow 236 at its juncture with the elbow 235 and extends generally horizontally. The box 259 has a hinged cover 260 secured thereto for access.

A resilient bag 261 is secured to the open end of the elbow 236 by means of a metallic clamp 262. The bag 261 is a thermal expansion and diaphragm action displacement bag which replaces the diaphragm 59 illustrated in FIG. 6.

The resilient bag 261 being resilient permits the fluid in the tube 231 to expand and contract under thermal conditions while retaining the diaphragm action required by the invention.

Having thus described the preferred embodiments of the invention it should be understood that numerous structural modifications and adaptations may be resorted to without departing from the spirit of the invention.

What is claimed is:

l. A hydraulic control system for controlling the position of a body member with respect to a support member wherein adjustable means on said support member support said body member, said adjustable means including means responsive to the flow of a control fluid pressure for moving said body member with respect to said support member about a horizontal axis; said control system comprising:

an elongated tube having end portions;

means sealing said end portions of said elongated tube, said sealing means including a flexible pressure responsive means mounted in one end of said elongated tube;

a fluid material substantially completely filling said elongated tube and in operative contact with said pressure responsive means so that said pressure responsive means moves responsive to the movement of said elongated tube about a transverse horizontal axis;

means mounting said elongated tube on one of said body member and said support member in a generally horizontal position, and generally transverse to said horizontal axis of movement of said body member with respect to said support member;

a fluid control valve having an inlet and at least one outlet, fluid control means in said valve for controlling the flow of fluid pressure from said inlet to said one outlet, said fluid control means including an actuating element;

a sourceof fluid pressure connected to said valve inlet;

linkage means coupling said actuator element to said pressure responsive means at said one end of said elongated tube such that said actuator element moves responsive to movement of said one pressure responsive means to regulate the amount of fluid pressure passing from said inlet to said one outlet;

means coupling said outlet of said valve to said adjustable means to supply a control pressure thereto, whereby shifting of said elongated tube from an equilibrium position results in control movement of said pressure responsive means to cause a corresponding movement of said actuator element and a flow of corrective fluid pressure to said adjustable support means, said adjustable support means responding to said flow of corrective fluid pressure to move said body member so as to return said elongated tube to said equilibrium position, and

grade applying means for changing the fluid equilibrium relationship between said support member and said fluid filled elongated tube so that a grade can be applied to said elongated tube with respect to said support member.

2. A hydraulic control system according to claim 1 wherein said mounting means includes a pivotable coupling of said elongated tube on said body member and said grade applying means includes a vertically adjustable coupling between said support member and said elongated tube for changing the angular relationship about said pivotable coupling between said support member and said elongated tube.

3. A hydraulic control system according to claim 1 wherein said control valve has a second outlet also coupled to said adjusting means, said adjusting means including means to move said body member in one angular direction with respect to said support member upon supply of fluid pressure from said first outlet, and means to move said body member in an opposite angular direction with respect to said support member upon receipt of fluid pressure from said second outlet, said actuation means controlling the flow of fluid to said first and second outlets.

4. A hydraulic control system according to claim 3 wherein said adjusting means includes a fluid cylinder with an extendable piston rod connected between said support means at one end and said body member at another end, and said one outlet is coupled to one end of said fluid cylinder and said second outlet is coupled to another end of said fluid cylinder.

5. A hydraulic control system according to claim 1 and further including a second pressure responsive means at the other end of said elongated tube; a second fluid control valve, said second fluid control valve having an inlet and at least one outlet, fluid control means in said second valve for controlling the flow of fluid pressure from said inlet to said outlet thereof, said fluid control means including an actuator element; said source of fluid pressure connected to said second valve inlet; linkage means coupling said second valve actuator element to said second pressure responsive means at said other end of said elongated tube such that said actuator element moves responsive to the movement of said second flexible pressure responsive means at said other end of said elongated tube to regulate the amount of fluid pressure passing from said inlet to said one outlet of said second valve; and means coupling said outlet of said second valve to said adjustable means to move said body member with respect to said support member about said axis to return said elongated tube to said equilibrium position.

6. A hydraulic control system according to claim 1 and further comprising a resilient thermo-expansion diaphragm displacement bag at the other end of said elongated tube, whereby said elongated tube is compensated for temperature changes.

7. A hydraulic control system according to claim 1 wherein said fluid control valve is mounted on said elongated tube adjacent said pressure responsive means. 

1. A hydraulic control system for controlling the position of a body member with respect to a support member wherein adjustable means on said support member support said body member, said adjustable means including means responsive to the flow of a control fluid pressure for moving said body member with respect to said support member about a horizontal axis; said control system comprising: an elongated tube having end portions; means sealing said end portions of said elongated tube, said sealing means including a flexible pressure responsive means mounted in one end of said elongated tube; a fluid material substantially completely filling said elongated tube and in operative contact with said pressure responsive means so that said pressure responsive means moves responsive to the movement of said elongated tube about a transverse horizontal axis; means mounting said elongated tube on one of said body member and said support member in a generally horizontal position, and generally transverse to said horizontal axis of movement of said body member with respect to said support member; a fluid control valve having an inlet and at least one outlet, fluid control means in said valve for controlling the flow of fluid pressure from said inlet to said one outlet, said fluid control means including an actuating element; a source of fluid pressure connected to said valve inlet; linkage means coupling said actuator element to said pressure responsive means at said one end of said elongated tube such that said actuator element moves responsive to movement of said one pressure responsive means to regulate the amount of fluid pressure passing from said inlet to said one outlet; means coupling said outlet of said valve to said adjustable means to supply a control pressure thereto, whereby shifting of said elongated tube from an equilibrium position results in control movement of said pressure responsive means to cause a corresponding movement of said actuator element and a flow of corrective fluid pressure to said adjustable support means, said adjustable support means responding to said flow of corrective fluid pressure to move said body member so as to return said elongated tube to said equilibrium position, and grade applying means for changing the fluid equilibrium relationship between said support member and said fluid filled elongated tube so that a grade can be applied to said elongated tube with respect to said support member.
 2. A hydraulic control system according to claim 1 wherein said mounting means includes a pivotable coupling of said elongated tube on said body member and said grade applying means includes a vertically adjustable coupling between said support member and said elongated tube for changing the angular relationship about said pivotable coupling between said support member and said elongated tube.
 3. A hydraulic control system according to claim 1 wherein said control valve has a second outlet also coupled to said adjusting means, said adjusting means including means to move said body member in one angular direction with respect to said support member upon supply of fluid pressure from said first outlet, and means to move said body member in an opposite anGular direction with respect to said support member upon receipt of fluid pressure from said second outlet, said actuation means controlling the flow of fluid to said first and second outlets.
 4. A hydraulic control system according to claim 3 wherein said adjusting means includes a fluid cylinder with an extendable piston rod connected between said support means at one end and said body member at another end, and said one outlet is coupled to one end of said fluid cylinder and said second outlet is coupled to another end of said fluid cylinder.
 5. A hydraulic control system according to claim 1 and further including a second pressure responsive means at the other end of said elongated tube; a second fluid control valve, said second fluid control valve having an inlet and at least one outlet, fluid control means in said second valve for controlling the flow of fluid pressure from said inlet to said outlet thereof, said fluid control means including an actuator element; said source of fluid pressure connected to said second valve inlet; linkage means coupling said second valve actuator element to said second pressure responsive means at said other end of said elongated tube such that said actuator element moves responsive to the movement of said second flexible pressure responsive means at said other end of said elongated tube to regulate the amount of fluid pressure passing from said inlet to said one outlet of said second valve; and means coupling said outlet of said second valve to said adjustable means to move said body member with respect to said support member about said axis to return said elongated tube to said equilibrium position.
 6. A hydraulic control system according to claim 1 and further comprising a resilient thermo-expansion diaphragm displacement bag at the other end of said elongated tube, whereby said elongated tube is compensated for temperature changes.
 7. A hydraulic control system according to claim 1 wherein said fluid control valve is mounted on said elongated tube adjacent said pressure responsive means. 